Cellular radio communication is an established technology wherein an area of communication coverage is divided into a plurality of cells. Each of the cells includes a base station equipped with a transceiver which communicates with mobile transceivers contained within the cell. The base station communicates with the mobile transceivers using radio frequency signals. Typically, the base station is linked to a communication network, such as a public telephone network, to provide an overall communication link between each mobile transceiver and the communication network.
Each cell has a boundary defined by an area of domination of a particular base station transmitter contained therein. The cells can range in size from a radius of one mile or less to 25 miles or more, with the size being determined by the transmitted signal power and the height of the antenna used by the base station. Although each cell is substantially dominated by a single base station, radio frequency signals from adjacent cells also propagate within each cell.
Problems of interference resulting from adjacent cell propagation arise when utilizing a cellular-type service within a building. The building may be divided into a plurality of microcells, wherein each microcell corresponds to a room or a floor of the building. The boundary of each microcell may defined by walls, a floor, and/or a ceiling of its corresponding room. Signals transmitted within one microcell may intrude into another microcell, which may be an adjacent floor or an adjacent room in the building. The escaped signals may then be received by unintended or unauthorized listeners. The lack of security which results is of particular importance in business communications conducted in proximity to competitors and potential eavesdroppers.